Oscillator circuit



May 15, 1962 F. J. KAEHNI OSCILLATOR CIRCUIT 3 Sheets-Sheet 1 Filed April 9. 1959 I773 INVENTOR.

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I 2 Frank J. Kaehni BY 8 a t 2 ms ATTORNE Ys May 15, 1962 F. J. KAEHN 3,035,108

OSCILLATOR CIRCUIT Filed April 9, 1959 3 Sheets-Sheet 2 TRI INVENTOR. Frank J. Kaehni MM/ )71 BY H/S ATTORNEYS May 15, 1962 F. J. KAEHNI 3,035,103

OSCILLATOR CIRCUIT Filed April 9, 1959 3 Sheets-Sheet 5 Fig.5

INVENTOR. Frank J. Kae/mi W, mmgiar MM HIS ATTORNEYS United States Patent Office 3,035,108 Patented May 15, 1962 Ghio Filed Apr. 9, 1959, Ser. No. 805,286 14 Claims. (Cl. 123-148) This application relates to oscillator circuits and, more particularly, to a push-pull oscillator embodying dual transistors for supplying power to a load. It forms a continuation-in-part of copending Kaehni application Serial No. 722,936, filed March 21, 1958, now Patent No. 2,968,296.

The present dual transistor circuits, several embodiments of which being hereinafter disclosed, employ power transistors of conventional make, and their use, preferably, is in the power supply to a sizeable high voltage load, operating with self-excited high frequency oscillations for purposes of that load. More specifically, they are primarily adapted for use as the power supply circuit for a high-voltage, high-frequency ignition system for spark ignition engines. The so-called continuous spark made available thereby, either individually to the engine cylinders in their firing order or else constantly to all cylinders in common, obviates the need for precise timing mechanism of the conventional type; in distinction to the single spark conventional with the latter mechanism, the spark of which characteristically weakens at higher speeds, a train of sparks created by the present circuit in compact succession to one another does not vary materially over the speed range of the engine and functions so effectively as to fire comparatively high air fuel ratio charges which can be run with up to 20% leaner carburetion at the lower speeds, compared to normal engine practices.

By providing self-excited dual transistors in the present oscillators and by operating them in push-pull to one another, I obviously obtain substantial power output, in some cases the consumption of these transistors jointly amounting to 3040 watts input power depending on requirements, and achieving exceedingly good overall efiiciency in the circuit. The transistors themselves are maintained in precisely opposite states of conduction as they oscillate under the excitations so that one delivers a current pulse to a high tension output transformer on first alternate half cycles of oscillation, whereas the other delivers a current pulse thereto on each remaining half cycle; similarly, each is held in nonconducting state on the alternate half cycle and thus neither is continuously conducting under the constant load of the transformer. I employ novel feedback means coupled directly to the load to obtain the precise stability and circuit control required and transistors thus equipped have been found to run cool and with the absence of excessive power peaks or spikes in the current flow on positive and negative cycles. In one of the presently disclosed embodiments of my invention, I provide capacitors in cross connections operatively between the transistors to serve as their feedback means. At high or low frequency operation, capacitors so connected as the feedback means also absorb the high voltage transients or spikes referred to which destroy transistors when present.

With the advent of transistors having higher voltage ratings and with high-tension output transformers having core materials of superior electromagnetic quality, it is possible to operate with relatively small values of capacitance and inductive reactance in the oscillator circuits presently employed. Relatively high frequencies are therefore obtainable with the power pulses produced, with consequent delivery of the desired high frequency, high output power.

As above indicated, the present oscillator circuits are adapted for supplying loads such as the step-up transformer in the ignition power supply of spark engines and, preferably, automotive engines; yet in broader concept, the present power amplifier-type circuits as adapted for this oscillator use find application with high frequency loads, in general, including but not limited to ones with predominantly capacitative, resistive, or mixed load characteristics and particularly the former in view of the capacitative character of the electrodes and the distributed capacity of the leads of the spark plugs supplied by the instantly disclosed transformer coil. There are numerous other uses, for example, in the broad field of radio, electronics, and power inverters; however, such applications will either be apparent to the reader or read ily suggest themselves when for a more detailed understanding of the invention, reference is made to the following description. In conjunction therewith, I have shown for purposes of illustration only, in the accompanying drawings, several embodiments of my invention. In the drawings:

FIGURE 1 is a schematic showing of an oscillator embodying the present dual transistor circuit;

FIGURES 2 and 3 are respectively the generalized and detailed showings of the oscillator of FIGURE 1 embodied in the ignition circuit of an automotive vehicle engine;

FIGURE 4 is similar to FIGURE 3 but shows a modified oscillator circuit; and

FIGURE 5 shows a further modification.

In FIGURE 1, I have illustrated a dual transistor oscillator circuit 10 in which the transistors TRl and TR2 are junction transistors of the p-n-p type. A l2-volt battery B has the positive terminal thereof connecting the emitters of the transistors in parallel, the emitter electrodes being indicated respectively by arrowheads. The collector electrode indicated by the numeral C of transistor TRI is connected through a collector output lead 11 to a coil terminal 12a on the primary winding of a step-up transformer "PF. Similarly, the collector electrode C of the transistor TR2 is connected through a collector output lead 13 to another coil terminal 12b on the primary winding which is center tapped at 14 thereby dividing the winding in two parts and returning the respective collector electrodes to a negative terminal on the battery B. A feedback capacitor 16a couples the collector electrode of the transistor TRI to the center or base electrode in the transistor TR2 and, similarly, a feedback capacitor 16b couples the collector and base electrodes of the respective transistors TR2 and TRl.

The collector electrodes 'C of the transistors are thus substantially negative with respect to the emitter electrodes, the emitters being the most positive electrodes in these transistors. A common return wire 15 from the center tap 14 has a portion connected to two base bias resistors 1 8a and 131) which respectively bias the base electrodes of the transistors TRI and TR2 with sufi'lcient direct negative current that they are held slightly negative with respect to the corresponding emitter electrode thereadjacent-for instance, to /2 volts therebelow under static or DC. conditions. It is important that the base bias resistors 18:: and 18b are thus returned to the terminal of the power source B, which in this case happends to be of negative polarity and which I have found produces the necessary high power capability with good low voltage starting as presently obtained.

Various makes of transistors are available which are suitable for this circuit and the hereinafter following circuits. Minneapolis Honeywells P-ll, Delco Remys types 2Nl74 and 2N290, and equivalent Motorola and Sylvania power transistors have been used with entirely satisfactory results.

Transistors TR1 and TR2 Two Delco-Remy 2N290 power transistors Base bias resistors 18a and 18b 200 ohms apiece Feedback capacitors 16a and 16b Each an 8 mf. electrolytic 12-turn center tap winding 5500 turns No. 37 wire Transformer TF primary Transformer 'I F secondary Transformer core material Allen Bradley W04 Ferrite Winding leg 1 /2" Side leg 1 /2" Leg diameter $1 The transistors TR1 and TR2 operate in push-pull in the foregoing circuit and for the loads contemplated and with the present low distributed capacity secondary winding, the oscillation frequency is in a range of 5,000 to 16,000 cycles per second. This frequency can be increased by reducing the size of the closed core 19 in the transformer TF, reducing current limiting capacitor 44 or reducing transformer winding turns.

The capacitors 16a and 16b serve to couple output of transistors to input base circuit in proper phase relationship to sustain an oscillating condition.

The repetitive charging and discharging of capacitor 16a in alternation with the capacitor 16b maintains the dual transistors in opposite states of conduction to one another and the cycles keep repeating as long as the battery B supplies the circuit. In one physically constructed embodiment of the invention, the transistors TR1 and TRZ drew 36 watts at 12 volts and supplied high frequency power to the high tension lead 40, the voltage thereof normally being maintained between 5,000 and 30,000 volts depending on character of the load L employed.

FIGURES 2 and 3 schematically show the oscillator of FIGURE 1 applied to an automotive vehicle ignition circuit in which an ignition switch 20 connects the parallel emitter electrodes of the transistors in circuit with the positive terminal of a car storage battery B. The battery B is located in the vehicle at one side of an engine compartment 22, defined at the rear by a usual fire wall 24 and at the front by a radiator core 26 used in the cooling system of the vehicle engine. The actual installation referred to above was in a 1957 Ford Skyliner sedan equipped with a left-hand drive having the usual steering column appearing at 33.

A metal plate 34 with fins of sulficient area to form a heat sink was mounted by electric insulating material 36 at a point in the air stream preferably forwardly of the radiator core '26 so as to initially receive the fiow of cooling air passing to the radiator core and cool and support the transistors TR1 and TRZ. Their self-generated heat was thus eliminated with no particular problem. The same support mounted the resistors and capacitors.

The transformer TF was mounted in the immediate vicinity of the engine so as to out down the length of the transformer and spark plug leads. The high-tension lead 40 from the transformer TF was permanently connected to the spark plugs 42 of the engine 30 through individual spark plug leads, each containing a current limiting capacitor '44. To eliminate radio interference, the transformer and spark plug leads are preferably shielded with shielded wiring connecting them together. Shields must be grounded. Bypass capacitors on battery leads and resistor-type spark plugs are also desirable where radio disturbance is to be completely eliminated in critical installations.

The inductance of the secondary winding and current limiting capacitors operate as a parallel resonant circuit when sparks occur and produce high voltages per turn of winding due to resonant conditions.

The spark plugs and capacitor 44 arrangement form no per se part of the present invention being separately disclosed and claimed in Kaehni application, Serial No. 675,652 filed August 1, 1957 now Patent No. 2,866,839 issued December 30, 1958 which in turn was a continuation in part of application Serial No. 567,777 filed February 27, 1956, now Patent No. 2,866,447 issued December 30, 1958. Briefly, however, the capacitors 44 consist of eight 10 to 20 M.M.F. capacitors, and they prevent the sparking conditions at one pair of electrodes in each spark plug 42 from adversely affecting simultaneous sparking at the other pairs. The spark plug gap setting is from 0.020 to about 0.040".

Alth ugh standard spark plugs may be used in FIG- URES 2 and 3, their electrodes will preferably be positioned within an ignition chamber or recess communieating with the main combustion chamber of each cylinder (not shown) to produce pre-combustion as a means of propagating the flame. Such pre-combustion chamber structure about the electrodes is indicated at 46 (FIG- URE 3); although physically formed separately from the combustion chamber and adapted to be threaded thereinto, it may be equally readily created through specially shaping upper portions of the cylinder wall or through use of a deeply recessed spark plug therein. Further details of the construction and specific characteristics of the inherently timed ignition process in the cylinders due to these continuous sparks is more completely set forth in Patent No. 2,866,839 just referred to.

It will be appreciated from an inspection of FIGURES 2 and 3 that the wiring of the resulting ignition circuit without a distributor being necessary has a considerably simplified form, with only two leads (collector current leads 11 and 13) being necessary between the transistor panel in its cooled frontal position and the transformer TF in its close operative position to the engine 30. The usual ground-return wires are omitted from the showing of the oscillator it in FIGURE 2 although schematically appearing in connection with the transformer TF of that figure.

in FIGURE 4 which shows a modified embodiment of the invention, a negative grounded battery B provides a l2-volt source of power which is connected through an ignition switch 20 and a center tap 14 to the two-part primary winding of a transformer TF. The primary winding has coil output terminals respectively indicated at 12a and 12b. The transformer TF has a core 19 on which a secondary winding is wound being grounded at one end and connected through a high tension lead 40 to a spark distributor 5% having an engine-driven rotor. I insert a resistance 51 to change the load L to a resistive load of a more desirable character than would prevail without the resistor and to reduce radio interference. The rotor of the distributor 50 does not require precise alignment when coordinated with the piston of the No. 1 cylinder of the engine 39 for reasons more fully set forth in parent application 722,946 previously referred to; in brief, the rotor shaft is common to the spark distributor 50 and to a centrifugal weight-operated mechanism 52 which is speed sensitive to automatically change the timing in relation to the speed.

It will be understood that the showing of the core 19 in the transformer TF of FIGURE 4 is purely schematicv and that in practice, a closed core will be used of a size which determines the proper power and frequency of sparks in the engine 30. The same core is common to the transformer primary winding and to a pair of feedback windings 54 and 55. The high-voltage secondary winding may be over the other windings on the same core leg to obtain good regulation.

The base bias resistors 18a and 1% are connected at one end to ground and at their opposite ends, they are connected through the respective feedback windings 54 and 55 to the base electrodes of dual transistors TR1 and TRZ. The coil terminals 120 and 1212 are connected through respective dropping impedances 60 to the emitter electrodes of the respective transistors. I have found this voltage dropping impedance 60 preferable, if not essential, to stabilize current flow to the transistors which would otherwise vary considerably as battery voltage fluctuations occur during operations such as cranking the vehicle engine by the battery B. The particular impedance selected consists of a temperature-compensated resistance whose characteristic is roughly inverse to that of the transistor so as to compensate for variations in resistance of the transistor caused by temperature variations.

A single shunt capacitance 56 is connected to the respective stabilizing resistors 60 and is operative within a maximum emitter-to-collector voltage ratings of the two transistors. The transistor TR2 couples the capacitance 56 in shunt between the emitter and collector electrodes of the transistor TRI. The transistor TRl serves an identical function during alternate half cycles of the pushpull oscillation. Thus, twice during each cycle of oscillation, the capacitor 56 protects a non-conducting transister from damage from countervoltage charges due to its limiting efiect on each peak inverse voltage. With higher voltage rating of transistor, the capacitance 56 may be omitted.

Closure of the ignition switch 20 in the circuit of FIGURE 4 sets the transistors TRI and TRZ into their push-pull operation, operating on feedback due to the inductive feedback windings 54 and 55 in contrast to the capacity feedback system of FIGURES 1-3 foregoing. The rotor in the spark distributor 50 has an extended width face so as to be in power transferring relation to an adjacent stationary contact in the distributor for a considerable arc of rotation of the distributor shaft. For this reason, the sparking in any one cylinder with which the rotor is aligned is substantially continuously maintained throughout a good portion of the compression and firing strokes of that cylinder.

In FIGURE 5, the dual transistor oscillator output circuit illustrated is based on the embodiment shown in FIGURE 4 except that a timer T1 has been added and a control winding 66 added to the core 19 of the transformer TF.

The transformer TF has a schematically shown core 19 which in practice is a closed core with all the Windings on one leg. The winding 66 thereof is electrically included in a loop circuit controlled by the timer T1 in a manner to intermittently short out the coils of that winding and control the amplitude of oscillations of the high frequency transformer TF due to its degenerative inductive coupling therewith. The timer T1 has a vacuum spark advance mechanism 68 operating from the intake manifold of a spark ignition engine 30 having eight cylinders as hereinabove illustrated. This spark advance automatically occurs on predetermined initial opening of the throttle (not shown) which thereupon exposes the mechanism 68 to intake manifold vacuum thus advancing the timing of the engine to fire the denser charges being admitted thereto. A rotor drive shaft 69 driven from the engine 30 in common to the cam of the timer T1 and to the rotor in a spark distributor 50 keeps the latter in mutually timed relationship to the engine.

Operation of the push-pull oscillator of FIGURE 5 in conjunction with the engine ignition circuit illustrated is more completely set forth in said parent application Serial No. 722,946. Briefly, however, when the points in the timer T1 are open, the high frequency generator circuit operates to supply high power output obtainable by using the dual transistors. A high potential secondary current flows through the secondary circuit owing to the small gap the rotor provides and a series of sparks occurs at the appropriate spark plug. The sparks occur at frequencies between about 3,000 and about 15,000 cycles 6 per second with the voltage at the plugs being maintained sufliciently high to maintain the continuous spark at the plug regardless of pressure in the cylinder.

The distributor 50 of FIGURE 5 may also have a fiyball governor advance mechanism associated with it for greater advance operation in high speed engines where a greater timing advance is desirable at the higher speeds.

When the points in the timer T1 close, the control winding 66 is shorted out. The output transformer TF supplies drastically reduced power, if any, to the spark distn'bu-tor 50 which, therefore is in essentially non-conducting relationship each time while it transfers into registry with the stationary distributor contact associated with the next spark plug to be fired. However, when the shorted coils of winding 66 are open circuited, the oscillations in the transformer resume with an instantaneous build up to full strength. Thus, the timer points Tl provide an accurately timed series of sparks for each specific cylinder.

If the user eliminates turns from the control winding component 66 so as to limit the number to a few turns or to one or two only, as actually illustrated in FIGURE 5, he can thus enable the transistor oscillator circuit to oscillate at reduced power while the timer points stay closed, impressing a low voltage corona condition across each spark plug gap to be fired beginning as soon as the rotor in the distributor 50 aligns at the proper position in power conducting relation. Thus, a high frequency corona is induced in the unfired charge adjacent the spark plug gap before its ignition and continues for the period ending on the instant at which the points open. This high frequency electrical energy adjacent the firing gap agitates and thoroughly mixes the combustion charge in that vicinity with the corona voltage being sufficiently low to prevent sparking at the plugs and at a frequency from 5,000 to 15,000 cycles per second depending upon the spark plug gaps and the compression ratio of the engine.

Modifications shown in the mechanical timed systems of FIGURES 4 and 5 also operate successfully in conventional engines which are not equipped with precombustion chambers when the initial timing is retarded approximately 10 to 20 degrees.

The foregoing embodiments of the present invention are found to satisfactorily ignite inducted fuel mixtures which are from 5 to 20% leaner than allowed under normal practices with domestic automotive engines and, thus, carburetor settings providing better economy are possible without detectable changes in engine smoothness. High speed operation under high power outputs and also the high vacuum engine idling conditions are equally satisfactorily performed using my ignition systems.

The transistor oscillator circuits of the preferred types illustrated have proved entirely satisfactory and in known manner may be arranged as common base, common emitter, or common collector types, all of which have been employed successfully. Storage batteries have been specifically referred to hereinabove, but other convenient sources of DC. voltage within the range of about 2 to about 30 volts are satisfactory for these circuits. In the embodiments of FIGURES 4 and 5 with the negative battery terminal grounded, I have used the grounded or common collector type of circuit. In FIGURE 1, the emitters of the dual transistors are connected in common to the positive terminal of the battery B. It is evident that the dual transistors composing each pair can equally well consist of complementary power transistors acting in push-pull for proper operation (requiring, however, modifications of the described circuits) instead of identical polarity power transistors (i.e., each one a p-n-p type) acting in push-pull as illustrated.

While I have shown and described several embodiments of this invention, it will be understood that they are illustrative only and that my invention may be embodied otherwise within the scope of the appended claims.

I claim:

1. An engine ignition system for supplying a plural spark plug load, of which the spark plugs are operatively connected with the cylinder means of the engine, comprising output transformer means for connection to said load having an output winding and an input winding, said transformer input winding having two parts connected in push-pull relation, transistor-type switch devices connected to said parts of said input winding and provided with mutual coupling means for maintaining said switch devices in opposite states of conduction relative to one another, a source of direct voltage and conductive means including said switch devices connecting said source in parallel relation to the parts of said input winding, so that current from said source flows alternately through one and the other of said parts, thereby delivering reversing flux input power to said transformer means, and means coupled in the output of said transformer means for distributing sparking power and connected to make sparking available at the individual spark plugs connected with the cylinder means.

2. Engine ignition system of claim 1, characterized by said mutual coupling means comprising feedback oscillator components and constituting the sole means controlling said switch devices so as to maintain a magnitude and frequency of alternating flux of substantial uniformity in said output transformer means.

3. Engine ignition system of claim 2, wherein said load is characterized by the incorporation of pairs of spaced electrode means individual to the plural spark plugs thereof, and further including conductive lead paths individual to said spark plugs, but with a common portion of the conductive paths connecting said distributing means to said transformer output for conducting the output thereof in common to said plugs as continuously supplied high frequency, high potential sparking current to each of their pairs of electrode means, said feedback oscillator components consisting of control capacitor means individual to and mutually controlling the operation of said switch devices to maintain uniform flux frequency and magnitude in the foregoing manner so as to keep said sparking current frequency substantially constant, and limiting capacitor means individual to the spark plugs for limiting current flow in said leads to each of their pairs of electrode means.

4. An engine ignition system according to claim 1 wherein said mutual coupling means comprises a feedback winding on said transformer means and having two parts each controlling a different switch device, the aforesaid distributing means of said system comprising a spark distributor having a controlled rotor frequency dependent on engine rotation and connected to said transformer means for delivering output power from the output winding thereof to the plural plugs in said load in timed relation to the engine.

5. Engine ignition system of claim 2 further characterized by said transistor-switch devices comprising t-ransistor means defining a first emitter-collector electrode path controlled by a first base electrode and second transistor means defining a second emitter-collector electrode path controlled by a second base electrode, said feedback oscillator components comprising capacitor means coupling said first base electrode to the collector electrode in said second emitter-collector path and coupling said second base electrode to the collector electrode in the first emitter-collector path in said transistor means.

6. An ignition system for a multi-cylinder engine, comprising in combination, spark plugs, a distributor connected thereto and together forming part of a spark plug load circuit, a transistor supply circuit including first transistor means with first base, emitter, and collector electrodes and second transistor means with second base, emitter, and collector electrodes, said transistor means having a common source of direct current and having individual first and second base bias resistors respectively,

and an output transformer inductively coupling the output of said transistor supply circuit to said distributor and including bipartite primary winding means and feedback winding means thereon, the two parts of said primary winding means being connected in series opposing relation so as to produce a push-pull operation in cou' pling said source respectively to said first collector and emitter electrodes and to said second collector and emitter electrodes, said feedback winding means providing for coupling said first base and emitter electrodes to said first base bias resistor, said feedback winding means further providing a similar coupling among said second base and emitter electrodes and said second base bias resistor.

7. Ignition system with the distributor and transistor supply combination of claim 6, characterized by one feedback winding providing said coupling in the transistor supply circuit on first alternate half cycles so as to enable one power pulse to flow therefrom through said primary winding means, and the other feedback winding providing said coupling on second alternate half cycles to enable an opposite power pulse to flow through said primary winding means, and a power delivery control component con-trolling output of said transistor supply circuit in a manner to impart different amplitudes of oscillation to said power pulses enabling the distributor to sequentially apply power to said spark plug load circuit in two stages.

8. Power supply means for a circuit with a plurality of spark plugs connected therein, comprising the combina tion with said spark plugs which plugs are arranged in said circuit for operating a multicylinder spark ignition engine, of a spark plug transformer included in and providing an inductive load in said circuit, push-pull oscillator having first transistor means with a first emitter-collector electrode path controlled by a first base electrode, and second transistor means with a second emitter-collector electrode path controlled by a second base electrode, a source of direct voltage having output terminals, said first and second emitter-collector paths having a common side connected to an output terminal of said source, the output terminals of said source being connected to conduct current alternately through said transistor means for supplying said inductive load, and feedback means providing for coupling said inductive load to the first base electrode for changing the base current enabling one transistor to conduct by being biased so as to render another transistor in non-conducting state on first alternate half-cycles, said feedback means further providing a similar coupling to the second base electrode for changing the base current enabling a different transistor to conduct by being biased so as to render the other one in the non-conducting state on second alternate half cycles.

9. Power supply means of claim 8 characterized by separate base bias resistors connected in parallel between the other named output terminal and the base electrode of each of said transistor means, said feedback couplings being connected to the base electrodes and to the corresponding bias resistors at the base connected end of the latter.

10. Power supply means of claim 8 characterized by said feedback couplings consisting of biasovercoming capacitors in cross connections between said transistor means and connected to different ones of the base electrodes thereof so as to be operative during discharge to hold each of the transistor means alternately in nonconducting state for half a cycle, and separate base bias resistors connected between the other named output terminal of said source and the base electrode of each of the transistor means operative upon substantial discharge of the associated capacitor to release that transistor means from its non-conducting state.

11. An air-cooled transistor power supply for the spark plug load of a spark ignition engine, said engine occupying an engine compartment defined by a radiator core confronting the engine at the forward end of the engine compartment and having a battery disposed in said compartment generally laterally to said radiator core and engine, said power supply comprising the combination of a push-pull transistor oscillator defining a plurality of emitter-collector paths; and provided with a heat conductive mass forming a heat sink common to the emitter electrodes of said emitter-collector paths, a transformer with a primary winding having a plurality of parts, conductive means for leading from said battery, operative to define separate collector current paths through said oscillator and connecting the output thereof to the parts of said primary Winding, electrically insulative means mounting the oscillator with said emitter heat sink exposed in the stream of cooling air being inducted into the engine compartment, and electrically insulative means mounting the transformer in said engine compartment in immediate vicinity to said engine, said transformer effective to couple the output of said oscillator to said spark plug load with a substantial stepup in voltage.

12. In an ignition system for the plural spark plug load of a multi-cylinder engine, an engine occupying an engine compartment defined by a radiator core confronting the engine at the forward end of the engine compartment, said engine being provided with a battery, the combination with said engine, of an air-cooled transistor power supply comprising a push-pull transistor oscillator defining dual emitter-collector paths, and provided with a heat conductive mass forming a heat sink common to two like electrodes of said emitter-collector paths, a transformer with a primary winding having a center tap dividing said winding into two parts, electrically conductive means of connection to said battery, operative to define separate, alternately conducting collector current paths through said oscillator and connecting the output thereof to different ones of the parts of said primary winding, electrically insulative means mounting the oscillator forward of the radiator core with said heat sink exposed in the stream of cooling air being inducted into the engine compartment, and electrically insulative means mounting the transformer in said engine compartment in proximate relation to the engine, said transformer having a secondary winding connected at one end to engine ground and having the opposite end connected in common to the plural spark plug load for concurrently delivering output of said oscillator to each plug continuously.

13. In an ignition system for the plural spark plug load of a multicylinder engine, the combination with a power output transformer, of means in circuit therewith for distributing sparking power effectively among individual spark plug loads connected in said cylinders and connected to make sparking avialable constantly to all cylinders in common, a battery, said transformer having a multipart first winding connected with one side of the battery in common to the first winding parts so as to form a portion of an input circuit and further having a second winding connected directly between the side of said battery common to the first winding parts and said distributing means, said first winding parts connected in a series opposing relation in said portion of the transformer input circuit, transistor-type switch devices connected to said parts and provided with mutual feed-back oscillator means for maintaining said switch devices in opposite states of conduction relative to one another, and conductive means including said switch devices for connecting said battery in parallel relation to the parts of said first winding, thereby completing said input circuit so that the current therein flows through the first Winding in bi-directional fashion alternately through one and the other of its parts.

14. In an ignition system for the plural spark plug load of a multicylinder engine, the combination with a power output transformer, of means in circuit therewith for distributing sparking power effectively among individual spark plug loads connected in said cylinders and connected to make intermittent sparking available individually to the engine cylinders in their firing order, a battery, said transformer having a multipart first winding connected with one side of the battery in common to the first Winding parts so as to form a portion of an input circuit and further having a second winding connected directly between the side of said battery common to the first winding parts and said distributing means, said first winding parts connected in a series opposing relation to said portion of the transformer input circuit, transistortype switch devices connected to said parts and provided with mutual feed-back oscillator means for maintaining said switch devices in opposite states of conduction relative to one another, and conductive means including said switch devices for connecting said battery in parallel relation to the parts of said first Winding, thereby complet ing said input circuit so that the current therein flows through the first winding in bi-directional fashion alternately through one and the other of its parts.

References Cited in the file of this patent UNITED STATES PATENTS 2,278,481 Peters et al Apr. 7, 1942 2,436,905 Short Mar. 2, 1948 2,774,875 Keonjan Dec. 18, 1956 2,843,744 Geyton July 15, 1958 2,847,489 Short Aug. 12, 1958 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,035, 108 May 15, 1962 Frank J. Kaehni It is hereby certified that error appears in the above numbered patent requiring correction and that the-said Letters Patent should read as corrected below.

read 722,946

I read happens column insert a Signed and sealed this 16th .day of October 1962.

SEAL) fittest:

IRNEST w. SWIDER DAVID LADD meeting Officer Commissioner of Patents 

